by Peter Sandercock
Plants need 17 essential nutrients in the soil to grow. Just as we need proper nutrition to stay healthy and grow, plants require nutrients from the soil to thrive. The most important nutrients for plants are nitrogen, phosphorus, and potassium. Each nutrient promotes different growth benefits so the advantage of fertilizer is that you can choose one that promotes root development or flowering or foliage growth. As a plant grows it extracts these nutrients from the soil, therefore they need to be replenished through fertilizers, rotted manure or compost each year.
Fertilizers have 3 numbers on the front label, separated by dashes. For example: 5-10-5. This is the fertilizer analysis or percentage by weight of the 3 major nutrients plants need: nitrogen, phosphorus and potassium. These are often abbreviated to N-P-K. When you purchased a 10-pound bag of fertilizer labeled 5-10-5, it would contain 5% nitrogen, 10% phosphorus and 5% potassium by weight. The remaining 80% could be comprised of other nutrients and filler.
- Nitrogen encourages foliage growth and green colour. If your plants turn light green it means they need nitrogen.
- Phosphorous contributes to many fundamental plant processes such as rooting and setting flower buds. It is especially important at the beginning of the growing cycle.
- Potassium contributes to the overall health and vigor of plants. It strengthens resistance to disease and stress.
- Other Ingredients: Any additional ingredients will be listed on the side label. This may include other nutrients like sulphur, calcium, magnesium, iron and other micronutrients. The label will also list the percentage of organic matter.
Always follow the label instructions when using any registered garden product. Just because a little is good, it doesn’t follow that a lot is better. To fertilize properly follow the 4Rs of fertilizer use: the right source at the right rate, the right time and the right place.
Right Source: Most garden centers will carry fertilizers especially formulated for you lawn or vegetable garden or flowers. You can also buy home soil kits to test your soil to see what it is lacking.
Hanging baskets and planters purchased at a greenhouse are usually grown in a light potting soil that contain peat moss, vermiculite and perlite. This mixture allows the roots to easily get established but doesn’t contain many nutrients for the plant and therefore must be fertilized frequently to ensure big beautiful blooms.
Right Rate: Know the size of your garden and lawn and only buy what you need. Use a lawn fertilizer spreader to ensure even coverage across your lawn. Uneven application can cause a variation in colour across your lawn or even potential burning if over applied. Never spread by hand.
Try to buy only what you need and use up the before the next season. If you have leftover fertilizer share it with others or store it tightly sealed in its original container (so you remember what it is and what it is for) in a dry place until the next season. Note: Five pounds of 10-20-10 would give you the same nutrient value as 10 pounds of 5-10-5.
Right Time: You can fertilize your lawn every month starting after the ground is no longer frozen in about April (depending where you live in Canada) up until the first frost in the fall. Some people use Canadian spring and summer holidays as reminders. Think Easter/Victoria Day, July 1st, Labour Day and Thanksgiving.
Right Place: After fertilizing, sweep any fertilizer off driveways, patios or sidewalks back onto you lawn or garden to prevent stray fertilizer from running off into the sewer or near by water bodies. This is because too much phosphorus in water can promote algae growth. Home owners that live by a pond, lake or stream should select phosphorus-free fertilizer.
- Some fertilizers also have weed control (think weed & feed) or insect and disease control products blended into them for added lawn and garden benefits.
- Healthy grass is great for the environment. A well established lawn absorb greenhouse gas, reduce soil erosion and produce oxygen! In fact, a 50-foot by 50-foot home lawn creates enough oxygen for a family of four every day!
- Learn more about the role of soil science in food production at Nutrients for Life.
- Farmers also follow the 4Rs of fertilizer use to ensure they get the most from their crops while not over using them and protecting the environment.